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Handling multiple slaves in a single I2C interface of DRA74xx

jeyaseelan kirubaharan
Expert 1330 points


Hi All,

We have a DRA74xx based board which runs QNX operating system. In one of the I2C interfaces we have 2 slave devices connected .One is touch controller and the other one is keys controller. How  should the software to be defined in the QNX side system. We have some a linux sample driver given for the touch interface from cypress semiconductor. But we do not have any driver present for key controller. Do we have to write 2 separate QNX drivers.In DRA7xx qnx bsp we see an atmel  mtouch driver is present and it is  mapped to another display driver of qnx . We need to replace it with cypress driver and have to write a custom key

driver for qnx. Is it possible to write two device drivers  over a single i2c interface. Also what could be the recommended architecture to be handling these 2 slave devices in a single i2c channel.

With regards,

Jeyaseelan

  • 0
    TI__Guru*** 125001 points

    Hi Jeyaseelan,

    Yes two different drivers, can control separate I2C devices on the same I2C bus.

    In the DRA74xx BSP, provided on qnx.com, in the sample build file provided (src/hardware/startup/board/dra74x/vayu-evm/build),  there is a an instance of the I2C driver started for each I2C bus that is used.  For example I2C bus 0 is launched with the following command:

    i2c-omap35xx-omap4 -p 0x48070000 -i 88 -c3 --u0

    This instance of the I2C driver (/dev/i2c0) can be used to communicate with all slaves on I2C0.

    There are examples in the BSP drivers of how the I2C driver can be used, see the src/hardware/mtouch folder for one example. 

    The documentation from QNX on the underlying software  interface is online here, or search on I2C in the QNX 6.6 documentation.

    Regards,

    kb

    .

  • 0 in reply to KB
    Expert 1330 points

    Thanks KB for the reply.

    We are planning to use mtouch driver only for handling the touch coordinates coming from one atmel slave device(slave-1) . On the same channel another slave device is connected for key&knobs sensing (slave-2).

    Is it possible for us to open and read   (/dev/i2c0) for using  slave -2  address from user level application of qnx  while mtouch is using slave-1 from qnx driver level. Or any new custom qnx driver has to be for written for slave-1 .Kindly clarify it the above design approach results in any conflicts at the i2c0 channel.

    With regards,

    Jeyaseelan

  • 0 in reply to jeyaseelan kirubaharan
    Expert 1330 points

    There is a typo in previous post.

    Thanks KB for the reply.

    We are planning to use mtouch driver only for handling the touch coordinates coming from one atmel slave device(slave-1) . On the same channel another slave device is connected for key&knobs sensing (slave-2).

    Is it possible for us to open and read   (/dev/i2c0) for using  slave -2  address from user level application of qnx  while mtouch is using slave-1 from qnx driver level. Or any new custom qnx driver has to be for written for slave-2 .Kindly clarify it the above design approach results in any conflicts at the i2c0 channel.

    With regards,

    Jeyaseela

  • 0 in reply to jeyaseelan kirubaharan
    TI__Guru*** 125001 points

    Hi Jeyaseela,

    Regarding "Is it possible for us to open and read   (/dev/i2c0) for using  slave -2  address from user level application of qnx  while mtouch is using slave-1 from qnx driver level. Or any new custom qnx driver has to be for written for slave-2".

    No additional S/W development is expected.  Please reference QNX I2C Documentation and the I2C driver included in the QNX BSP, under .../src/hardware/i2c.

    Regards,

    kb

  • 0 in reply to KB
    Expert 1330 points

    Hi KB,

    Thanks for the clarifications.

    We just go ahead and develop user level application by opening /dev/i2c0 instance for slave-2, that is for keys & knobs.

    With regards,

    Jeyaseelan